Solar Array Layout Calculator

About the Solar Array Layout Calculator

Calculates how many solar panels fit in a string within an inverter's voltage window, and the total panels and power for your array.

How to use this calculator

1. Enter the panel specification values, especially the maximum system voltage, the panel open-circuit voltage, and the temperature adjustment if needed.
2. Enter the inverter or charge controller voltage limit and the target array size.
3. Calculate the maximum panels per string, then determine how many strings are needed for the total number of panels.
4. Check that the final layout stays within electrical limits before using the design in the field.

The formula explained

The main calculation finds the maximum number of panels that can be placed in one string without exceeding the allowed voltage, using the panel voltage and any cold-weather adjustment. It also helps determine the total number of strings needed for a given panel count.

• n = maximum panels per string
• \(V_{max}\) = maximum allowed system or inverter voltage
• \(V_{oc}\) = panel open-circuit voltage
• \(N_{total}\) = total number of panels in the array
• \(N_{strings}\) = number of strings needed

Step by step method

1. Find the effective panel voltage used for sizing, including any temperature adjustment if the tool requires it.
2. Divide the allowed voltage by the effective panel voltage to estimate the maximum number of panels per string.
3. Round down to the nearest whole number, because you cannot use part of a panel.
4. Divide the total number of panels by the panels per string to find the number of strings, then round up if there is any remainder.

Worked example

Problem. A solar setup has an inverter limit of \(600\) volts, each panel has an open-circuit voltage of \(40\) volts, and the array uses \(13\) panels total. How many panels can go in each string, and how many strings are needed?

1. Compute panels per string: \(n = \\frac{600}{40} = 15\).
2. Check the total array size: \(\\frac{13}{15} = 0.866...\), so one string is enough.
3. Use \(13\) panels in a single string, since that stays under the limit of \(15\) panels per string.

Tips and common mistakes

• Always round panels per string down, not up, because going over the voltage limit can damage equipment.
• If temperature affects panel voltage, use the coldest expected condition for the safest layout.

Frequently asked questions